Detection of histidine rich protein 2 and panmalarial ICT Malaria Pf/Pv test antigens after chloroquine treatment of uncomplicated falciparum malariadoes not reliably predict treatment outcome in eastern Indonesia

In regions with drug-resistant malaria, the ability to rapidly detect or pr edict treatment failure (TF) soon after a course of standard therapy for Pl asmodium falciparum malaria would facilitate the prompt institution of seco nd-line therapy. We thus evaluated longitudinally the ability of the ICT Ma laria Pf/Pv immunochromatographic test to predict treatment outcome. Sixty- six Sumbanese Indonesians with uncomplicated falciparum malaria were treate d with chloroquine and followed for 28 days by use of 1997 World Health Org anization criteria for assessment of therapeutic efficacy of antimalarial d rugs. The ICT Pf/Pv testing could be compared with microscopy in approximat ely half of the patients on each day of follow-up. Although strongly positi ve histidine rich protein 2 (HRP2) line intensities (equal to or greater th an the control band) in convalescence were highly predictive of TF any degr ee of positivity for the HRP2 and panmalarial antigens in convalescence was only moderately predictive of TF. Positive predictive values of the HRP2 a nd panmalarial antigens for TF were 76.9% and 87.0%, respectively, on Day 3 , 82.4% and 87.5% on Day 7, and 78.9% and 78.9% on Day 14. Negative HRP2 an d parimalarial antigen results in convalescence were even less predictive o f an adequate clinical response, and false-negative HRP2 and panmalarial an tigen test results were found in one-sixth (6 of 37) of recrudescent infect ions diagnosed by microscopy among patients with late treatment failure. To reliably predict treatment outcome with rapid antigen tests, further devel opment appears necessary to improve sensitivity for viable asexual parasite s while avoiding detection of both gametocytes and persistent antigen in co nvalescence.